<template>
	<view class="u-scroll-list" ref="u-scroll-list">
		<!-- #ifdef APP-NVUE -->
		<!-- nvue使用bindingX实现，以得到更好的性能 -->
		<scroller class="u-scroll-list__scroll-view" ref="u-scroll-list__scroll-view" scroll-direction="horizontal"
			:show-scrollbar="false" :offset-accuracy="1" @scroll="nvueScrollHandler">
			<view class="u-scroll-list__scroll-view__content">
				<slot />
			</view>
		</scroller>
		<!-- #endif -->
		<!-- #ifndef APP-NVUE -->
		<!-- #ifdef MP-WEIXIN || APP-VUE || H5 || MP-QQ -->
		<!-- 以上平台，支持wxs -->
		<scroll-view class="u-scroll-list__scroll-view" scroll-x @scroll="wxs.scroll" @scrolltoupper="wxs.scrolltoupper"
			@scrolltolower="wxs.scrolltolower" :data-scrollWidth="scrollWidth"
			:data-barWidth="$u.getPx(indicatorBarWidth)" :data-indicatorWidth="$u.getPx(indicatorWidth)"
			:show-scrollbar="false" :upper-threshold="0" :lower-threshold="0">
		<!-- #endif -->
			<!-- #ifndef APP-NVUE || MP-WEIXIN || H5 || APP-VUE || MP-QQ -->
			<!-- 非以上平台，只能使用普通js实现 -->
			<scroll-view class="u-scroll-list__scroll-view" scroll-x @scroll="scrollHandler"
				@scrolltoupper="scrolltoupperHandler" @scrolltolower="scrolltolowerHandler" :show-scrollbar="false"
				:upper-threshold="0" :lower-threshold="0">
			<!-- #endif -->
				<view class="u-scroll-list__scroll-view__content">
					<slot />
				</view>
			</scroll-view>
			<!-- #endif -->
			<view class="u-scroll-list__indicator" v-show="indicator" :style="[$u.addStyle(indicatorStyle)]">
				<view class="u-scroll-list__indicator__line" :style="[lineStyle]">
					<view class="u-scroll-list__indicator__line__bar" :style="[barStyle]"
						ref="u-scroll-list__indicator__line__bar"></view>
				</view>
			</view>
	</view>
</template>

<script src="./scrollWxs.wxs" module="wxs" lang="wxs"></script>

<script>
	/**
	 * scrollList 横向滚动列表
	 * @description 该组件一般用于同时展示多个商品、分类的场景，也可以完成左右滑动的列表。
	 * @tutorial https://www.uviewui.com/components/scrollList.html
	 * @property {String | Number}	indicatorWidth			指示器的整体宽度 (默认 50 )
	 * @property {String | Number}	indicatorBarWidth		滑块的宽度 (默认 20 )
	 * @property {Boolean}			indicator				是否显示面板指示器 (默认 true )
	 * @property {String}			indicatorColor			指示器非激活颜色 (默认 '#f2f2f2' )
	 * @property {String}			indicatorActiveColor	指示器的激活颜色 (默认 '#3c9cff' )
	 * @property {String | Object}	indicatorStyle			指示器样式，可通过bottom，left，right进行定位
	 * @event {Function} left	滑动到左边时触发
	 * @event {Function} right	滑动到右边时触发
	 * @example
	 */
	// #ifdef APP-NVUE
	const dom = uni.requireNativePlugin('dom')
	import nvueMixin from "./nvue.js"
	// #endif
	import props from './props.js';
	export default {
		name: 'u-scroll-list',
		mixins: [uni.$u.mpMixin, uni.$u.mixin, props],
		// #ifdef APP-NVUE
		mixins: [uni.$u.mpMixin, uni.$u.mixin, nvueMixin, props],
		// #endif
		data() {
			return {
				scrollInfo: {
					scrollLeft: 0,
					scrollWidth: 0
				},
				scrollWidth: 0
			}
		},
		computed: {
			// 指示器为线型的样式
			barStyle() {
				const style = {}
				// #ifndef APP-NVUE || MP-WEIXIN || H5 || APP-VUE || MP-QQ
				// 此为普通js方案，只有在非nvue和不支持wxs方案的端才使用、
				// 此处的计算理由为：scroll-view的滚动距离与目标滚动距离(scroll-view的实际宽度减去包裹元素的宽度)之比，等于滑块当前移动距离与总需
				// 滑动距离(指示器的总宽度减去滑块宽度)的比值
				const scrollLeft = this.scrollInfo.scrollLeft,
					scrollWidth = this.scrollInfo.scrollWidth,
					barAllMoveWidth = this.indicatorWidth - this.indicatorBarWidth
				const x = scrollLeft / (scrollWidth - this.scrollWidth) * barAllMoveWidth
				style.transform = `translateX(${ x }px)`
				// #endif
				// 设置滑块的宽度和背景色，是每个平台都需要的
				style.width = uni.$u.addUnit(this.indicatorBarWidth)
				style.backgroundColor = this.indicatorActiveColor
				return style
			},
			lineStyle() {
				const style = {}
				// 指示器整体的样式，需要设置其宽度和背景色
				style.width = uni.$u.addUnit(this.indicatorWidth)
				style.backgroundColor = this.indicatorColor
				return style
			}
		},
		mounted() {
			this.init()
		},
		methods: {
			init() {
				this.getComponentWidth()
			},
			// #ifndef APP-NVUE || MP-WEIXIN || H5 || APP-VUE || MP-QQ
			// scroll-view触发滚动事件
			scrollHandler(e) {
				this.scrollInfo = e.detail
			},
			scrolltoupperHandler() {
				this.scrollEvent('left')
				this.scrollInfo.scrollLeft = 0
			},
			scrolltolowerHandler() {
				this.scrollEvent('right')
				// 在普通js方案中，滚动到右边时，通过设置this.scrollInfo，模拟出滚动到右边的情况
				// 因为上方是用过computed计算的，设置后，会自动调整滑块的位置
				this.scrollInfo.scrollLeft = uni.$u.getPx(this.indicatorWidth) - uni.$u.getPx(this.indicatorBarWidth)
			},
			// #endif
			//
			scrollEvent(status) {
				this.$emit(status)
			},
			// 获取组件的宽度
			async getComponentWidth() {
				// 延时一定时间，以获取dom尺寸
				await uni.$u.sleep(30)
				// #ifndef APP-NVUE
				this.$uGetRect('.u-scroll-list').then(size => {
					this.scrollWidth = size.width
				})
				// #endif

				// #ifdef APP-NVUE
				const ref = this.$refs['u-scroll-list']
				ref && dom.getComponentRect(ref, (res) => {
					this.scrollWidth = res.size.width
				})
				// #endif
			},
		}
	}
</script>

<style lang="scss" scoped>
	@import "../../libs/css/components.scss";

	.u-scroll-list {
		padding-bottom: 10px;

		&__scroll-view {
			@include flex;

			&__content {
				@include flex;
			}
		}

		&__indicator {
			@include flex;
			justify-content: center;
			margin-top: 15px;

			&__line {
				width: 60px;
				height: 4px;
				border-radius: 100px;
				overflow: hidden;

				&__bar {
					width: 20px;
					height: 4px;
					border-radius: 100px;
				}
			}
		}
	}
</style>